Food storage buckets are packed with ease of use in mind. Each meal is separately sealed in mylar pouches so that you can eat the amount of food that you need while still maintaining sealed pouches for future meals. Whereas with #10 cans, once you open the can, you've got about 1 week to consume the entire contents of the can before the food goes bad.
In other words, if you are feeding a larger family, the food buckets or #10 cans are just fine because you will probably eat the entire contents of a can within a few days. But if you a feeding only 1-3 people, the food buckets are designed for you because you can better pick and choose which meals and how much of the meals you are eating.